In the known machines, groups designed for the preparation and dispensing of beverages generally comprise a collecting device having a seat that receives a disposable cartridge.
Since the disposable cartridges are originally sealed to avoid spillage of the soluble product during handling, the collecting device is generally fitted with a piercing member that opens one or more outlet openings on one wall of the cartridge (for example, on the base wall of the same) in correspondence to a plurality of pre-established breaking lines.
Once the cartridge is inserted into the appropriate seat on the collecting device, water is admitted under pressure to the inside of the cartridge through an entry port of the same in order to form a beverage consisting of a suspension or dispersion in water of the soluble product, which is dispensed through an outlet opening or hole located on the cartridge. A dispensing group must guarantee complete and uniform solubilization or suspension/dispersion of the product in the fluid (usually water) inside the cartridge and good final appearance of the beverage; in the case of coffee and cappuccino good final appearance means being “creamy”, i.e. having an appreciable amount of a layer of enduring small-bubble froth. Obtaining such a result is complicated by the fact that the shape and dimensions of the cartridge are the same for all products dispensed, while the amount of soluble product in the cartridge varies dramatically from product to product (for example: 1.5 grams for espresso coffee and 15-16 grams of product for chocolate and cappuccino). This variation in amount affects the capacity to solubilize the product homogeneously. Another problem of the known dispensing groups is guaranteeing thorough cleaning of the group; this requires avoiding the use of dispensing conduits and tubes with section less than 2 mm, because of the risk of formation of coatings and residues in the same.
In a previous patent application, still pending, in the name of the same Applicant, it is suggested to provide a throttling arrangement along the dispensing course of the beverage with the aim of improving the mixing of the soluble product with the water admitted to the cartridge and to creating a pressure gradient inside the cartridge so as to obtain a good quality beverage with attractive appearance on delivery. This has been achieved by means of a piercing member having a diameter greater than the diameter of the product outlet opening: the pressure of the water on arrival in the cartridge determines solubilization and delivery of the beverage.
However, it has been found that the beverage obtained is not always optimum, in particular with respect to the amount and duration of cream produced.